Control system



Get. 4, 1938. c, STEWART 2,132,277

CONTROL SYSTEM Filed Feb. 12 1937 Inventor: Clyde )2. StQWlTt,

Patented Oct. 4, 1938 PATENT OFFICE cou'mor. srs'ram Clyde E. Stewart, Upper Darby, Pa assignor to General Electric Company, a corporation of New York Application February 12, 1937, Serial No. 125,404

6 Claims.

My invention relates to control systems and particularly to a. system for controlling a rapidly operating device such as a rotary selector switch so that it may be positively stopped in any of a plurality of its positions, and one object of my invention is to provide an improved control system for accomplishing this result.

My invention will be better understood from the following description when taken in connection with the accompanying drawing, the single figure of which diagrammatically illustrates a rotary selector switch control system embodying my invention, and its scope will be pointed out in the appended claims.

Referring to the accompanying drawing, I represents a rotary selector switch 0! any suitable type, examples of which are well known in the'art. As shown in the drawing, the switch includes a bank of stationary contacts 2 and a co-operating movable wiper 3 which is arranged to be moved into engagement with successive contacts by a ratchet 4 that is operated in any suitable manner each time an associated operating magnet 5 is de-energized.

In accordance with my invention, I provide an improved operating control circuit for the magnet 5, whereby when a starting circuit is completed for the winding 9 of the magnet 5, the winding Sis intermittently energized to' move the wiper 3 to a desired contact and when the wiper engages this desired contact,the circuit of the magnet 5 is controlled in such a manner as to insure that the wiper 3 remains on the desired stationary contact. For accomplishing this result, I provide a control relay 6 which has two diflerential windings I and I. The winding I is connected in parallel with the winding 3 of the operating magnet 5 and the winding 3 is connected in series with the parallel connected windings I and 9 by the normally closed contacts ll of the operating magnet 5. 'Also a resistor II is connected in parallel with the winding I 01' the relay 6 by the normally closed contacts l2 oi' the relay 6. A suitable start switch i3 is provided which when closed supplies the operating potential to the circuit of the magnet winding 9.

Since the operating magnet 5 requires a relatively large current to operate it, the resistance of the energizing circuit of this magnet has to be relatively low. This result is obtained by making the resistance of the resistor ll relatively low, The resistance of the windings I. and 3 are made relatively high so that during the stepping operation of the operating magnet I only a small current flows through these two diilerential windings and these two windings are also designed so that the resultant ampere turns produced by these small currents flowing through them during the stepping operation of the operating magnet 6 are substantially zero in order to insure that the relay 8 remains in itsnormally de-energized position.

Associated with each stationary contact 2 is a circuit closing device ll which, when closed, connects the associated contact 2 to the source of control current so that when the wiper engages the contact 2 a low resistance shunt circuit is completed around the parallel connected windings I and 9. This shunt circuit reduces the voltage drop across the winding 9 oi the magnet I so that it cannot pick up and consequently further movement of the wiper 3 is prevented as long as the circuit closing device It associated with the contact 2 with which the wiper 3 is in engagement remains closed. The closing of the shunt circuit around the winding 1 of the relay 6 also increases the voltage impressed across the winding 3 so that the resultant ampere turns produced by the two diiferential windings I and 8 are increased to a sufllcient value to cause the relay .6 to open its contacts i2 and thereby disconnect the resistor II from across the control source. Since the resistance of the winding 8 is materially greater than the resistance of the resistor II, the control source has to supply only a small current to maintain the switch in any of its oil-normal positions.

The operation of the arrangement shown in the drawing is as follows: It will be assumed that the switch I is in its normal position as shown, and that it is desired to cause the wiper 3 to engage one of its oil-normal contacts 2. The

circuit closing device H associated with this de-' sired ofl-normal contact 2 is closed so as to connect the positive terminal of the control source directly to this contact 2. Then the start switch I3 is closed to complete a circuit from the positive terminal of the control source through the switch ii, the windings 9 and 1 in parallel, the contacts iii of magnet 5, and then to the negative terminal oi the control source through the winding I of relay 6, and also through the contacts l2, and resistor il in series. The current in this circuit is suflicient to cause the magnet 5 to operate and open its contacts iii. The currents through the windings l and 8, however, are such that the ampere turns of the two windings are substantially equal and opposite and therefore the relay does not operate to open its contacts l2. The opening oi the contacts l0 effects the de-energization oi the magnet 5, which in returning to its de-energized position, operates the ratchet 4 to move the wiper 3 from its normal position to its first oil-normal position. As soon as the magnet 5 has reached its normal position and has closed its contacts 10, the heretofore described clrcuit through the windings 9, I, 8 and resistor II is again completed. In this manner, the magnet 5 is intermittently energized and deenergized until the wiper 3 engages the contact 2 which is connected directly to the positive terminal of the control source by its associated circuit closing device l4. When the wiper 3 engages this contact 2, a low-resistance shunt circuit is completed around the windings I and 9 so that substantially the full potential of the control source is impressed across winding 8 of the relay 6. Consequently, the magnet 5 is prevented from operating but the relay 6 operates to open its contacts I! and disconnect the resistor H from across the control source.

The relay 6 may also be providedwith other contacts l6 which may be connected in any suitable manner so as to effect the operationof another control device (not shown) which it is desired to operate when the switch I has stopped in an off-normal position.

While I have, in accordance with the patentstatutes, shown and described my invention as applied to a particular system and as embodying various devices diagrammatically indicated,

changes and modifications willbe obvious to those skilled in the art, and I therefore aim in the ap-' tacts, means including a magnet for moving said wiper into successive engagement with said contacts, a winding for saidmagnet, a control relay having two differential windings, means for completing an" energizing circuit for said magnet winding with one of said relay windings connected in parallel with said magnet winding and the other of said relay windings connected in series withsaid magnet winding, means responsive to the energization of said magnet for opening said energizing circuit, and means for closing a shunt circuit around said parallel connected magnet and relay windings when said wiper engages a predetermined contact.

2. In combination, a rotary switch having a movable wiper and a plurality of stationary contacts, means including a magnet for moving said wiper into successive engagement with said contacts, a winding for said magnet, a control relay having two diiferential windings, means for completing an energizingcircuit for said magnet with one of said relay windings connected in parallel with said magnet winding and the other of said relay windings connected in series with said magnet winding, contacts in said energizing circuit, means responsive to the energization of said magnet for opening said last mentioned contacts, a parallel circuit around said other of said relay windings including an impedance, contacts in said parallel circuit controlled by said relay, and means for closing a shunt circuit around said parallel connected magnet and relay windings when said wiper engages a predetermined contact.

3. In combination, a rotary switch having a movable wiper and a plurality of stationary contacts, a magnet, a winding for said magnet, means including said magnet for moving said wiper into successive engagement with said contacts, a control relay having two difierential windings of relatively high impedances, means for completing an energizing circuit for said magnet winding with one of said relay'windings connected in parallel with said magnet winding and the other of said relay windings connected in series with said magnet winding, contacts in said energizing circuit, means responsive to the energization of said magnet for opening said last mentioned contacts, and means for closing a shunt circuit around said parallel connected magnet and relay windings when said wiper engages a predetermined contact.

4. In combination, a rotary switch having a.

movable wiper and a plurality of stationary contacts, a magnet, means including said magnet for moving said wiper into successive engagement with said contacts, a winding for said magnet, a

i control relay having two differential windings of relatively high impedances, means for completing an energizing circuit for. said magnet winding with one of said relay windings connected in parallel with said magnet winding and the other of said relay windings connected in series with said magnet winding, contacts in said energizing circuit, means responsive to the energization of said magnet for opening said last mentioned contacts, a parallel circuit around said other of said relay windings including a relatively low impedance device, contacts in said parallel circuit controlled by said relay, and means for closing a shunt circuit around said parallel connected magnet and relay windings when said wiper engages a predetermined contact.

5. In combination, a rotary switch having a movable wiper and a plurality of stationary contacts, means including a magnet having a relatively low resistance winding for moving said wiper into successive engagement with said contacts, a control relay having two differential windings of relatively high substantially equal resistances, a resistor having a relatively low resistance value, means for completing an energizing circuit forv said magnet winding with one of said relay windings connected in parallel with said magnet winding and the other of said relay windings connected in series with said magnet winding and said resistor connected in parallel with said other of said relay windings, contacts in said energizing circuit connected in series with said relay windings, means responsive to the energization of said magnet for opening said last mentioned contacts, means for closing a shunt circuit around said parallel connected magnet and relay windings when said wiper engages a predetermined contact, contacts in series with said resistor in the parallel circuit around said other of said relay windings, and means for opening said last mentionedcontacts when a predetermined unbalance occurs in the energizations of said relay windings.

6. In combination, a rotary switch having a movable wiper and a plurality of stationary contacts, means including a magnet for moving said wiper into successive engagement with said contacts, a winding for said magnet, means for completing a circuit including said magnet winding,

means responsive to the energization of said magnet for opening said circuit, means for completing a shunt around said. magnet winding when said wiper engages a predetermined contact, and means controlled by said magnet for increasing the resistance in said circuit after said shunt is completed.

CLYDE E. STEWART. 

